Carborane Promoted New Ring Transformations

摘要

Previously, we demonstrated a method for introduction of carborane moiety into 1,2,4-triazine cycle by the reaction of nucleophilic substitution of hydrogen in 1,2,4-traizine-4-oxides 1. In this case, a σ-adduct 2 is re-aromatised by treatment with mild acylating agent (DMCC) yielding a 5-carboranyl 1,2,4-triazine 3. Unexpectedly, when we changed an acylating agent and used acetyl chloride, no aromatization occurred but a ring transformation took place. In the case of Ar = aryl, the carboranyl triazoline 4 was obtained. If Ar was 2-pyridyl, the 2-carboranyl imidazo[1,5a]pyridine 5 was formed.